This book describes the impact, stability and designs of dams, which are based upon structural, geotechnical and hydraulic properties. The impact of the dam structure on the upstream and downstream catchments are considered: e.g., sediment trap, fish migration, downstream water quality, and modifications of the water table and associated impacts (salinity). The impact dams have on the survival of certain fish is also reviewed. For example, dams impact the survival of juvenile anadromous fishes by obstructing migration corridors, lowering water quality, delaying migrations, and entraining fish in turbine discharge. To reduce these impacts, structural and operational modifications to dams- such as voluntary spill discharge, turbine intake guidance screens, and surface flow outlets are instituted. These data on the operational and structural changes to the dams for the benefit of anadromous fish populations are examined. This book also describes the bankfull hydraulic geometry adjustments caused by check dams. The concrete-face rockfill dam (CFRD), a simple dam type which has remarkable ecomical, ecological and environmental benefits, is analysed as well, as it has become one of the most widely used dam types. Finally, this book explores two aspects related to the environmental impacts that trigger the construction of hydrological correction check dams: the erosion caused within the riverbeds and the ploughing and soil movements made by the opening of paths in order to grant access to the check dams.